This looks to be an excellent prospect.? https://aseba.wikidot.com/en:thymio
The development environment looks reasonably good and the cost of the Robot itself is around ?85.00 (converted from Swiss Francs). As mentioned in the IEEE article below, for less than ?1000 you could kit a whole class room out with these devices and the software is free.
I am certainly tempted to get one for "my nephew".?